Heart valve disease is a widespread condition in which one or more of the valves of the heart fails to function properly. Diseased heart valves may be categorized as either stenotic, wherein the valve does not open sufficiently to allow adequate forward flow of blood through the valve, or incompetent, wherein the valve does not close completely, causing excessive backward flow of blood through the valve when the valve is closed. A heart valve may also be both stenotic and incompetent. Valve disease can be severely debilitating and even fatal if left untreated, particularly if the diseased valve is the mitral valve (between the left atrium and left ventricle) or the aortic valve (between the left ventricle and the aorta). According to recent estimates, more than 80,000 patients are diagnosed with aortic or mitral valve disease in U.S. hospitals each year.
Various surgical techniques may be used to repair a diseased or damaged valve. One repair technique which has been shown to be effective in treating incompetence, particularly of the mitral and tricuspid valves, is annuloplasty, in which the effective size of the valve annulus is contracted by attaching a prosthetic annuloplasty ring to an interior wall of the heart around the valve annulus. The annuloplasty ring comprises an inner substrate of a metal such as stainless or titanium, or a flexible material such as silicone rubber or Dacron cordage, covered with a biocompatible fabric or cloth to allow the ring to be sutured to the heart tissue. The annuloplasty ring may be stiff or flexible, may be split or continuous, and may have a variety of shapes, including circular, D-shaped, C-shaped, or kidney-shaped. Examples are seen in U.S. Pat. Nos. 4,917,698, 5,061,277, 5,290,300, 5,350,420, 5,104,407, 5,064,431, 5,201,880, and 5,041,130, which are incorporated herein by reference.
Using current techniques, most valve repair and replacement procedures require a gross thoracotomy, usually in the form of a median sternotomy, to gain access into the patient's thoracic cavity. A saw or other cutting instrument is used to cut the sternum longitudinally, allowing two opposing halves of the anterior or ventral portion of the rib cage to be spread apart. A large opening into the thoracic cavity is thus created, through which the surgical team may directly visualize and operate upon the heart and other thoracic contents. Alternatively, a thoracotomy may be performed on a lateral side of the chest, wherein a large incision is made generally parallel to the ribs, and the ribs are spread apart and/or removed in the region of the incision to create a large enough opening to facilitate the surgery.
Using such open-chest techniques, the large opening provided by a median sternotomy or right thoracotomy enables the surgeon to see the mitral valve directly through the left atriotomy, and to position his or her hands within the thoracic cavity in close proximity to the exterior of the heart for cannulation of the aorta and/or coronary arteries to induce cardioplegia, manipulation of surgical instruments, removal of excised tissue, and introduction of an annuloplasty ring or a replacement valve through the atriotomy for attachment within the heart. However, these invasive, open-chest procedures produce a high degree of trauma, a significant risk of complications, an extended hospital stay, and a painful recovery period for the patient. Moreover, while heart valve surgery produces beneficial results for many patients, numerous others who might benefit from such surgery are unable or unwilling to undergo the trauma and risks associated with open-chest procedures.
Annuloplasty ring prostheses are generally mounted on a holder assembly to facilitate their manipulation during the course of a surgical intervention and their implantation. Current holder assemblies are characterized by a number of drawbacks. A great majority of holders are configured with a rigid handle and a fixed orientation of the holder body or prosthesis carrier relative to the handle. Such a mechanical limitation does not allow the surgeon to orient the holder body relative to the handle in order to optimize the delivery of the prosthesis to the implant site. Some holder assemblies have been configured with malleable handles in an attempt to alleviate this drawback. However, such malleable handles are generally difficult to reshape in different bent configurations once they have been initially bent. Some holder assemblies have introduced shape memory alloys, such as Nitinol, for the material of the handle. Handles made from Nitinol that would be bent during the surgical procedure would resume their straight unbent shape after being exposed to sterilization temperatures. However, Nitinol handles are expensive and may be too easy to bend out of desired shape when the cardiac prosthesis mounted on end of such handles is exposed to tissue or suture loads during the surgical intervention.
In view of actual and perceived drawbacks associated with current annuloplasty techniques, there is a need for a less invasive approach and improved handle.